The invention relates to a blood chamber for use in an extracorporeal circuit.
Specifically, though not exclusively, the invention can be usefully applied for realising an arterial chamber of a dialysis set.
In particular, reference is made to a chamber made according to the preamble of the accompanying first claim.
A chamber of this type is known, for example from U.S. Pat. Nos. 4,681,606 and 5,769,815.
U.S. Pat. No. 4,681,606 teaches a blood chamber, made in a single piece by plastic material blow-forming and comprising: a blood inlet port arranged inferiorly; a blood outlet port arranged superiorly; a service port, arranged superiorly, for connection with an external monitoring system of the pressure in the chamber; a containment chamber having a blood inlet which is arranged lying vertical at about halfway up the containment chamber, and a vertically-lying outlet on the bottom of the containment chamber; an inlet conduit extending from the inlet port to the inlet; and an outlet conduit extending from the outlet to the outlet port. The bottom wall of the containment chamber is inclined towards the outlet and joins a lower edge of a lateral wall of the containment chamber with a lower edge of the outlet.
The inlet conduit extends vertically in an upwards direction, being laterally connected with the containment chamber, and exhibits an end tract which deflects inwardly of the containment chamber, forming a curve of about 90°. Normally the blood fills the containment chamber up to a higher level than the inlet. As the blood flow at inlet of the containment chamber is essentially horizontally-directed, any blood spray is directed towards the opposite lateral wall from the inlet, and not upwards, especially not towards the upper service port. Any air bubbles contained in the blood which enter the chamber are transported upwards towards the free surface of the blood, and then enter the gaseous atmosphere situated above the blood surface. The blood at the inlet of the containment chamber is subject to slowing by effect of the increase of the section of the containment chamber with respect to the section of the inlet conduit, with a consequent reduction of the air bubble drawing effect, so that the air bubbles can more easily rise to the surface by effect of hydrostatic thrust.
U.S. Pat. No. 5,769,815 discloses a blood chamber having an inlet port which is superiorly arranged, separate and distanced laterally from the containment chamber. The inlet port communicates with a central zone of the chamber through a descending lateral conduit which, at an end thereof, bends transversally to guide the blood flow so that it enters the chamber in a more-or-less horizontal direction through an inlet. The containment chamber exhibits, in front of the blood inlet, an inclined abutment which deviates the blood flow upwards in order to define a gentle circular flow in the upper part of the containment chamber. The chamber of U.S. Pat. No. 5,769,815 is usable in particular as a venous chamber of a dialysis circuit.
The prior art further comprises U.S. Pat. No. 4,428,743 which discloses a blood chamber, usable for example as a drip chamber or an expansion chamber, provided with a deflector for directing the blood flow from an inlet to an outlet of the containment chamber, in which the deflector is formed by a recess in the wall which delimits the chamber.
The deflector has the essential function of conveying the blood along a delicate and gentle pathway, so as to safeguard the blood, and especially to avoid platelet damage, while at the same time preventing the formation of foam. The chamber, in this case, is preferably formed in a single body by blow-forming of plastic material. The blood inlet port and the blood outlet port are both arranged at a lower end of the chamber. Both the inlet port and the outlet port exhibit a vertical axis. The connection conduit, which connects the blood inlet port with the inlet in the containment chamber, is essentially vertical and straight.
The deflector is located immediately above the inlet. The inlet is arranged obliquely, while the outlet is arranged horizontally. The containment chamber is inferiorly delimited by a bottom wall which joins a lower edge of the inlet with a lateral edge of the outlet.
The prior art also includes U.S. Pat. No. 5,643,205 which discloses an arterial blood chamber for a hemodialysis set, made in a single piece by blow-forming of a plastic material, destined for direct connection with a tract of arterial line (pump segment) engaged to the peristaltic blood pump. The chamber is provided with a lower access port connected to a containment chamber by a short conduit, and with an upper access port which is connected to the containment chamber by a vertically-extended conduit, by the side of the containment chamber and remotely connected to the containment chamber. The chamber can be used both upstream of the blood pump (in which case the pressure in the chamber is negative i.e. sub-atmospheric), and downstream of the blood pump (with positive i.e. above atmospheric pressure). If the chamber is used before the blood pump, the lower port is the blood inlet port and the upper port is the blood outlet port, and the case is vice versa if the chamber is downstream of the blood pump.
Blood chambers in the prior art exhibit some limitations and drawbacks.
Firstly, the fluid dynamics of the blood can be improved to further reduce the formation of foam, especially internally of the containment chamber, and to convey the blood along a gentle pathway in order to reduce stress on the blood itself.
Secondly, the effectiveness of the separation of the gassy parts from the blood can be improved upon.
Furthermore, some of the blood chambers in the prior art, in order to guide the blood in a gentle and regular flow, exhibit a relatively high lateral volume.